Omeprazole is an inhibitor of gastric acid secretion making it useful as an antiulcer agent U.S. Pat. No. 4,255,431 (corresponding to EP 0 005 129) discloses a process for the preparation of this class of substituted benzimidazoles. Said process comprises a couple of reaction steps. The three last steps of the process utilize more than one solvent and requires isolation of intermediates to give the final product omeprazole. The resulting product is contaminated with starting materials and by-products.
WO 91/18895 describes an improved process for synthesis of omeprazole. This process describes the oxidation step and a work-up procedure of omeprazole. The oxidation step utilizes m-chloroperoxybenzoic acid in a methylene chloride/water system at substantially constant pH of about 8.0 to 8.6. The work-up procedure includes crystallization of omeprazole by the addition of an alkyl formate.
Another process for the manufacture of omeprazole is described in U.S. Pat. No. 5,391,752. This process also describes only the oxidation step. Said oxidation step utilizes magnesium monoperoxyphtalate as an oxidazing agent. The resulting product is contaminated with starting material and by-products.
Yet another process for the manufacture of compounds showing structural similarities to omeprazole is disclosed in U.S. Pat. No. 4,619,997. The intermediates are isolated, but not purified, and different solvent systems are used in the chemical steps throughout the process.
In the light of the above there was still a need for a new convenient and more efficient process to manufacture omeprazole.